Project description:Nutritional immunology: Diversification and diet-dependent expression of antimicrobial peptides in the Black soldier fly Hermetia illucens
Project description:Contamination of food products with mycotoxins such as aflatoxin B1 (AFB1) poses a severe risk to human health. Larvae of the black soldier fly (BSFL), Hermetia illucens (Diptera: Stratiomyidae), can successfully metabolize AFB1 without any negative consequences on their survival or growth. However, the underlying mechanisms that allow BSFL to metabolize AFB1 are unknown. In this study, five-day-old BSFL were fed with either a control or an AFB1-spiked (20 µg/kg) diet to elucidate the underlying mechanisms. Larval samples were collected at three timepoints (6 h, 24 h, and 72 h) and subjected to RNA-Seq analysis to determine gene expression patterns. Provision of an AFB1-spiked diet resulted in an up-regulation of 357 and a down-regulation of 929 unique genes. Upregulated genes include multiple genes involved in AFB1 metabolism in other (insect) species. Downregulated genes were generally involved in the insects' growth, development, and immunity. BSFL possesses a diverse genetic arsenal that encodes for enzymes capable of metabolizing AFB1 without trade-offs on larval survival.
Project description:Black soldier fly larvae meal (BSFL) from Hermetia illucens is a promising alternative protein source in diets for farmed fish. The larvae can efficiently convert low-value organic material into high quality protein in a production cycle with low arable land and freshwater inputs. A few recent studies have shown that BSFL is a suitable protein source for Atlantic salmon (Salmo salar) in smaller controlled experiments. However, industry-relevant field trials conducted under large scale near-commercial conditions over a longer period are lacking. In this study, a feeding trial was performed to evaluate the impact of BSFL on growth performance and health of Atlantic salmon during the grow out phase in seawater, in a commercial site in Vestland county, Norway. A total of 320,000 post-smolt Atlantic salmon were distributed into six duplicate sea cages and fed one of three diets (commercial-like control diet and two test diets partially replacing the protein content of the control diet with 4 % and 8 % defatted BSFL meal) for 21 weeks, until a relevant commercial slaughter size of 4.5-5.0 kg was reached. Health parameters were assessed including histology of the distal intestine (DI), in addition to DI microbiota identification (by 16s rRNA-seq) and salmon RNA-seq of DI and head kidney (HK). The results showed that the inclusion of BSFL meal supported growth performance and had no adverse effect on gut health. The beta diversity of the distal intestine microbiota and the relative abundance of families Lactobacillaceae and the chitinolytic Bacillaceae increased in the fish fed the BSFL diets. Additionally, no histopathological changes were attributable to BSFL meal intake. Results from RNA-seq in DI revealed that BSFL inclusion modulates metabolic processes associated with lipids, the response to estrogens, the activity of immune receptors (to chemokines), phagocytosis and extracellular vesicles. Based on these results, black soldier fly larvae meal is a suitable alternative protein ingredient in inclusions of up to at least 8 % for Atlantic salmon under industrial fish farming conditions.
